Not sure what's causing it but i've noticed when posting when posting from a High latency connection I seem to end up double posting.

Chrome, On OSX 10.8.3
T-mobile HSPA
VPN'd via openvpn (Bypasses their awful transparent proxies)

Latency is about 200 - 4000ms

Also tends to be intermittent packet loss depending on the Load on the local Cell and the signal strength